Compounds containing a perfluorooxyalkylene moiety generally have a very small surface free energy and, accordingly, have good water- and oil-repellency, chemical resistance, lubricity, a releasing property, and an antifouling property. Taking advantage of these properties, they are widely used as, for example, water- and oil-repellent agents or antifouling agents for paper and fiber, lubricants for magnetic storage media, oil-repellent components for precision apparatuses, releasing agents, cosmetics, and protective coatings. Recently, there is an increasing need for technology to attain fingerprint proofness or easy removal of fouling on a surface of a display for better appearance or visibility. Perfluorooxyalkylene compounds are used as a material to meet these requirements. In particular, perfluoropolyethers comprising (CF2O) units are preferable because of their good lubricity. For instance, FOMBLIN Z type [(CF2O)p(CF2CF2O)q] is commercialized. However, FOMBLIN Z type has wide molecular weight distribution, so that a polymer synthesized from the FOMBLIN Z type perfluoropolyether has a wide temperature range of vaporization. Therefore, there is a problem such that properties of a coating vary depending on vacuum deposition conditions. Further, it is difficult to control a degree of vacuum and a temperature rise rate of a surface treatment agent, so that properties of a coating vary among batches even when the same apparatus is used.
Japanese Patent Application Laid-Open Nos. 2011-116947, 2012-233157 and 2012-72272, hereinafter called Patent Literatures 1 to 3, discloses surface treatment agents comprising a composition which comprises a mixture of a fluorooxyalkylene group-containing polymer whose main chain is —(OC2F4)e(OCF2)fO— and which has a hydrolysable group at one terminal, and a fluorooxyalkylene group-containing polymer having hydrolysable groups at the both terminals, wherein an amount of the fluorooxyalkylene group-containing polymer having hydrolysable groups at the both terminals is specified. Patent Literatures 1 to 3 also describe that the surface treatment agents can form a water- and oil-repellent layer having excellent scratch resistance and a lower dynamic friction coefficient.    Patent Literature 1: Japanese Patent Application Laid-Open No. 2011-116947    Patent Literature 2: Japanese Patent Application Laid-Open No. 2012-233157    Patent Literature 3: Japanese Patent Application Laid-Open No. 2012-72272